1. Field of the Invention
The present invention relates to an image forming apparatus such as a laser printer or a digital copy machine, and more particularly to an image forming apparatus controlled and operated in accordance with a program which is read out at the start of the operation.
2. Description of the Related Art
A conventional electronic instrument, such as an image forming apparatus having a nonvolatile memory (e.g. an EPROM or a ROM) which stores programs, such as control programs, used for image processing has been proposed. In the conventional electronic instrument, various processes are executed in accordance with the programs.
When the contents of the programs should be corrected because of defects such as bugs, the nonvolatile memory should be changed. In a work to change the nonvolatile memory, the apparatus has to be disassembled to be capable of changing the memory. Thus, a large amount of time is required for the work to change the memory.
In the recent years, to decrease the working time required to update the programs in the nonvolatile memory, it has been proposed that a flash ROM is used as the nonvolatile memory storing the programs. In order to update the programs, updated programs are down loaded from an external storage unit, such as an IC card, to the flash ROM. Thus, the working time required to update the programs can be greatly decreased.
For example, in an apparatus disclosed in Japanese Laid Open Patent Application No.8-83175, an external memory in which a control program for changing the contents in a flash memory and contents to be changed are stored is used. When the external memory is connected to a connector of the apparatus, addresses of the flash memory and the external memory are switched. The apparatus is then started up by the program in the external memory so that the contents in the flash ROM is changed.
In an apparatus disclosed in Japanese Laid Open Patent Application No.9-258976, two ROMs having the same capacity are provided. In each of the two ROMS, a down loading control program and a control program are stored. A chip select circuit is operated so that the control program in a ROM is changed by the down loading control program in another ROM. In addition, in an apparatus disclosed in Japanese Laid Open Patent Application No.6-222924, an address of a ROM detachable from the apparatus is specified by pull-down resisters or pull-up resisters connected to an address bus. A boot program in the ROM mounted in the apparatus is executed so that a control program supplied from an external unit is written in a flash memory. After this, the ROM is detached from the apparatus.
In addition, an IC card may be also used to supply an optional program and/or data to an apparatus having a flash memory. The optional program and/or data are added to a data table of a program stored in the flash memory so as to be used for an optional function of the apparatus. Due to change of the IC card, various optional programs and/or data may be used in the apparatus. In this case, a user can use various functions other than the standard specification.
In the conventional apparatus, the IC card is mainly used for the down loading operation to change a program stored in the flash ROM. When a connection of the IC card to the apparatus is detected, a boot process for the program stored in the IC card is executed so that the down loading operation is performed.
However, if an IC card storing an optional program and/or data as described above is connected the apparatus, when the connection of the IC card to the apparatus is detected, the optional program and/or data stored in the IC card is used to start the process. In this case, the apparatus is not started up and not operated by the program stored in the flash memory.
Accordingly, a general object of the present invention is to provide a novel and useful image forming apparatus in which the disadvantages of the aforementioned prior art are eliminated
A specific object of the present invention is to provide an electronic instrument in which a process can be started even if an external storage unit (e.g., an IC card) storing any information (a program used by a processing unit to start the process, data, optional programs or the like) is connected to the instrument.
The above objects of the present invention are achieved by an electronic instrument having a nonvolatile rewritable memory in which a program is stored, a connector to which an external storage unit is connectable, and a processing unit which starts a process using a program stored in the nonvolatile rewritable memory or the external storage unit connected to the connector, the electronic instrument comprising: a connection detector detecting whether the connector is connected with the external storage unit; an operation unit, operated by an operator, outputting an operating signal having one of first and second states in accordance with an operation of the operator; a boot selection controller selecting a device to be booted from the nonvolatile rewritable memory and the external storage unit in accordance with a detection result obtained by the connection detector and a state of the operation signal from the operation unit so that the processing unit starts the process using the program stored in the booted device; and a determination unit whether the external storage unit stores a program to be used by the processing unit to start the process when the external unit is selected as the device to be booted, wherein the boot selection controller comprises: a first control unit selecting the external storage unit as the device to be booted when the connection detector detects that the external storage unit is connected to the connector and the operation unit outputs the operating signal having the first state; and a second control unit changing the device to be booted from the external storage unit selected by the first control unit to the nonvolatile rewritable memory when the determining unit determines that the external storage unit does not stores the program and the operation unit outputs the operating signal having the second state.
In the electronic instrument according to the present invention, if the external storage unit is connected to the connector, the operator operates the operation unit so that the operation signal having the first state is output by the operation unit. As a result, the first control unit of the boot selection controller selects the external storage unit as the device to be booted. In this case, if a program to be used by the processing unit to start the process is stored in the external storage unit, the processing unit starts the process using the program stored in the external storage unit. On the other hand, if a program to be used by the processing unit to start the process is not stored in the external storage unit, the determination unit determines that the external storage unit does not store the program to be used by the processing unit to start the process. In this case, if the operator operates the operation unit so that the operating signal having the second state is output by the operation unit, the booted device is changed from the external unit to the nonvolatile rewritable memory by the second control unit. As a result, the processing unit starts the process using the program stored in the nonvolatile rewritable memory.
Thus, the processor can start the process regardless of whether the external storage unit connected to the connector stores the program to be used by the processing unit to start the process or other information.